"These tribes, which defended Islam throughout all of its history, will not give up to one slave of America," the speaker says.

There was no independent confirmation that the voice on the tape was that of Zawahiri, an Egyptian-born physician who is al Qaeda's No. 2 figure.

The voice on the tape also calls Musharraf a traitor and "Muslim assassin."

"After he played his deceiving role in killing thousands of Muslims in Afghanistan, the Americans began giving him new duties," the voice says.

The speaker says Musharraf is helping the United States and its allies "suppress the Muslim nation" by cutting support for Islamic militants in Kashmir and betraying Pakistan's nuclear secrets.

In recent weeks, large numbers of Pakistani forces have moved into the mountainous tribal areas, where U.S. intelligence officials suspect Zawahiri and bin Laden may have taken refuge.

Last Thursday, Musharraf -- a key U.S. ally in the war on terrorism -- said Pakistani troops had cornered a "high-value target" in the region, and other Pakistani officials said they suspected that target was Zawahiri. But they backed away from those reports as the standoff and fighting continued through the weekend.

The voice on the tape does not mention the region where the fighting has been taking place, Waziristan, but it does mention two different tribes of the area.

In Washington, a U.S. official said the CIA is analyzing the tape to determine whether it's authentic. The official said the tape is being compared with other known examples of Zawahiri's speech, and a judgment is likely within two days.

The tape appears to have been recorded later than February, when Pakistan's military sent large numbers of troops into the mountainous tribal areas along Pakistan's border with Afghanistan in a crackdown against suspected al Qaeda and Taliban members.

The tape attempts to appeal to Pakistanis' pride by saying that surprise searches, arrests and other operations being conducted by the Pakistani military along the border are insulting, according to Octavia Nasr, CNN senior editor for Arab affairs, who reviewed the recording. The voice urges residents of the region to stand up for themselves.

The 52-year-old al-Zawahiri, an Egyptian national, is considered to be Osama bin Laden's closest adviser and is viewed by many analysts as the operational brains behind the al Qaeda terror network.

Al-Zawahiri is one of the most-wanted terrorists in the United States. He was indicted along with bin Laden for his alleged role as mastermind of the 1998 bombings of the U.S. embassies in Kenya and Tanzania that killed 224 people.

U.S. government sources also believe he played a significant role in the September 11, 2001, attacks.